The methodology for the synthesis of hydrolytically stable dideoxy nucleo- sides, considered to be of potential use as anti-HIV agents, has been extended to various modified purine and pyrimidine bases. The 2'-fluoro substituent in the ara-configuration protects these compounds against chemical as well as enzymatic degradation. Some of the new compounds synthesized appear to function as "prodrugs" which require the action of adenosine deaminase to uncover their biological activity. A new synthetic approach toward fluorine-containing dideoxynucleosides was developed. It greatly facilitates the process since a critical reductive step is now performed before the condensation reaction. This reaction is used only once for the production of many compounds, rather than every time a new compound is prepared. A series of dideoxyapiose nucleosides is being developed as potential anti-HIV agents. These compounds were designed as partial structures of the ring expanded analogue of the antibiotic oxetanocin.